The below has been tested on exchange 2010 to export calendar permissions for mailboxes in a specific OU.
# Get the mailboxes
$Mailboxes = get-mailbox -OrganizationalUnit “OU=Users,DC=Contoso,DC=local” -Filter {RecipientTypeDetails -eq “usermailbox”} -ResultSize Unlimited
# An array for the output
$Output = @()
# Loop through the mailboxes
ForEach ($Mailbox in $Mailboxes) {
# Get the name of the calendar folder
$Calendar = (($Mailbox.PrimarySmtpAddress.ToString())+ “:\” + (Get-MailboxFolderStatistics -Identity $Mailbox.DistinguishedName -FolderScope Calendar | Select-Object -First 1).Name)
# Get the permissions on the folder
$Permissions = Get-MailboxFolderPermission -Identity $Calendar
# Loop through the permissions, populating the output array
ForEach ($Permission in $Permissions) {
$Permission | Add-Member -MemberType NoteProperty -Name “Mailbox” -value $Mailbox.DisplayName
$Output = $Output + $Permission
}
}
# Write the output to a CSV file
$Output | Select-Object Mailbox, User, {$_.AccessRights}, IsValid | Export-Csv -Path C:\temp\Calendarpermissions.csv -NoTypeInformation
Filtering to the specific OU is very useful if you are managing multi-tenant exchange environment. Modify the above script as per your needs and save as .ps1 to run on powershell.
Exchange KB 